1. Field of the Invention
The present invention relates to a tunneling magnetoresistive element that may be installed in hard disk drives or magnetic detectors, and more particularly, it relates to a tunneling magnetoresistive element that can achieve a high rate of resistance change (ΔR/R).
2. Discussion of the Related Art
Tunneling magnetoresistive (TMR) elements generate a resistance change by utilizing a tunneling effect. When the magnetization direction of a pinned magnetic layer is antiparallel to the magnetization direction of a free magnetic layer, less tunneling current flows through an insulating barrier layer (tunnel barrier layer) disposed between the pinned magnetic layer and the free magnetic layer, and thereby the resistance reaches its peak. On the other hand, when the magnetization direction of the pinned magnetic layer is parallel to the magnetization direction of the free magnetic layer, the tunneling current reaches the maximum, and the resistance reaches the minimum.
According to this principle, an external magnetic field changes the magnetization of the free magnetic layer and thereby changes the electrical resistance. The tunneling magnetoresistive elements detect the change in electrical resistance as a voltage change and thereby detect a leakage magnetic field from a recording medium.
Japanese Unexamined Patent Application Publication No. 2006-261637 discloses a tunneling magnetoresistive element that includes a free magnetic layer having a layered ferri structure.
In this patent document, the free magnetic layer includes ferromagnetic layers and a first orientation control buffer disposed between the ferromagnetic layers to generate large exchange coupling. A free magnetic layer including Ni81Fe19 (2 nm)/Ta (0.4 nm)/Ni81Fe19 (2 nm)/Ru (2.1 nm)/Ni81Fe19 (4 nm) laminated in that order from the bottom is disclosed in paragraph [0139].
However, this patent document does not disclose a structure that can achieve a high rate of resistance change (ΔR/R).